The present invention concerns piping used in aircraft refuel systems. More particularly, this invention concerns a pipe comprising an outer section making up a pipe wall, the pipe wall having an outer and inner surface. The invention also concerns a method of manufacturing piping for an aircraft refuel system.
Conventional refuel piping is manufactured from aluminium and extruded in lengths to suit the required fuel tank geometry. Brackets are used, wherever needed, in order to brace pipework. Fittings and adaptors are used to accommodate fuel system equipment, such as valves. FIG. 1 shows a typical prior art fuel system piping configuration. This configuration includes a high number of parts, has a high weight and is costly to manufacture.
In the piping configuration of FIG. 1, the manufacturing method used and the materials used result in internal skin imperfections on the inside of the pipe. This increases the roughness of the inside of the pipe and increases the skin friction as the wetted area of the inside of the pipe is increased. In order to minimise the skin friction in the pipes, the inside of the pipe bore can be polished. However, this manufacturing process is not particularly practicable as the cost of the polishing process is high and it is not possible to achieve a perfectly smooth bore pipe.
Any skin friction generated in the pipes, results in inefficiencies in the refueling process. This makes refueling slower, resulting in increased turnaround time and subsequent cost for the aircraft operator. The refuel equipment also requires more power for a given speed of refuel. This is sometimes not possible and, in any case, increases the cost for the refueling operator.
The present invention seeks to mitigate the above-mentioned problems. Alternatively or additionally, the present invention seeks to provide an improved pipe for an aircraft refuel system. Alternatively or additionally, the present invention seeks to provide an improved method for manufacturing pipe for an aircraft refuel system.